Night-Time Transpiration – Favouring Growth?

Plants loose water at significant rates during the night through ‘night-time transpiration’. Night-time transpirational water loss is most likely the consequence of having respiratory CO2 escape at sufficiently high rates through stomata. As night-time respiration fuels growth and depends on daytime provision of storage carbohydrates, there must exist some regulation, involving the internal clock, between daytime photosynthesis and growth, and night-time transpiration and growth. Night-time growth presents a more efficient use of taken up water for leaf cell expansive growth compared with daytime growth, and could represent an overlooked stress acclimation process. Plants grow and transpire water during the day and night. Recent work highlights the idea that night-time transpirational water loss is a consequence of allowing respiratory CO2 to escape at sufficiently high rates through stomata. Respiration fuels night-time leaf expansion and requires carbohydrates produced during the day. As carbohydrate availability and growth are under the control of the plants’ internal clock, so is night-time transpiration. The cost of night-time transpiration is that water is lost without carbon being gained, the benefit is a higher efficiency of taken up water for use in leaf expansion. This could provide a stress acclimation process. Plants grow and transpire water during the day and night. Recent work highlights the idea that night-time transpirational water loss is a consequence of allowing respiratory CO2 to escape at sufficiently high rates through stomata. Respiration fuels night-time leaf expansion and requires carbohydrates produced during the day. As carbohydrate availability and growth are under the control of the plants’ internal clock, so is night-time transpiration. The cost of night-time transpiration is that water is lost without carbon being gained, the benefit is a higher efficiency of taken up water for use in leaf expansion. This could provide a stress acclimation process. a plant hormone best known for its role in regulating stomatal aperture and originally thought to be responsible for the controlled loss (abscission) of leaves; also present in animal tissues. chemical formula CO2. A colourless gas, which has no electric dipole character and forms a weak acid (carbonic acid, H2CO3) when dissolved in water; a major chemical substrate for photosynthesis, and a product of respiration. the irreversible increase of physical size of cells; requires net intake of water and solutes, and in walled cells, such as plant cells, a wall which yields to the hydrostatic pressure within cells. a chemical structure which covers the aerial organs of plants and consists of a matrix (cutin), and a material (waxes), which is embedded in or deposited onto this matrix; main diffusion barrier for gases, such as water vapour and CO2, between plant internal and external air space. day/night changes; in a 24 h context, also referred to as ‘circadian’. an organism’s biological time setter for circadian processes, which allows these processes to continue even in the absence of external diurnal (light/dark) period changes. in the broadest physiological sense, a metabolic pathway through which the degradation (use) of nutrients results in the release of energy; can be anaerobic and aerobic, with the latter in mitochondria requiring unlimited gas (O2, CO2) exchange. small openings in the surface of aerial plant organs, which can be opened/closed reversibly; enable plants to regulate the exchange of gases, particularly water vapour and CO2, with the environment in the short-term and long-term. nonstructural carbohydrates in plants, such as starch and fructans, which allow the build-up of large amounts of (typically) hexose monomers, through polymerisation, without causing excessive osmotic forces and associated water intake; major source of carbon and energy in many plant tissues at times where photosynthetic carbon and energy assimilation is not possible (e.g., roots, dark period). the evaporative loss of plant internal water from aerial plant surfaces, such as leaves; can occur through stomata and cuticle.